Jekyll and Hyde
noun [ S ] disapproving uk/ˌdʒek.əl ənd ˈhaɪd/ us/ˌdʒek.əl ənd ˈhaɪd/
具有善恶双重人格的人，双重性格交替出现的人
a person with two very different sides to their personality, one good and the other evil
The professor was a real Jekyll and Hyde - sometimes kind and charming, and at other times rude and obnoxious. 这位教授真是个双重性格的人——有时和蔼可亲，有时粗暴而惹人讨厌。